Textured surfaces of physical objects have been used to encode information.
For example, a compact disc (CD) may encode audio information using tiny indentations (called pits) and areas between pits (called lands) on the surface of the CD. In a conventional CD, a transition between a pit and a land (or vice versa) may encode a 1, while no change may indicate a zero or string of zeroes.
A phonograph has a textured surface that encodes analog audio data. Braille uses patterns of bumps (e.g. embossments) to encode letters, punctuation and words. For example, if a 3 row by 2 column array of Braille positions has only one bump in the upper left corner of the array, and no other bumps in the array, then the array of positions encodes an “a” or a “1” in Braille.
The rotational position of triangular data glyphs has been used to encode information. Some data glyphs are embossed or engraved.